Catalytic desulfurization of crude petroleum hydrocarbons



June 30, 1959 F. w. B. PORTER ET AL 2,892,774

CATALYTIC DEISULFURIZATION 0F CRUDE PETROLEUM HYDROCARBONS Filed Jan. 22, 1953 INVENTORS:

FREDERICK WILLIAM BERTRAM PORTER ROY PURDY NORTHCOT'I ATTORNEYS United tates Patent CATALYTIC DESULFURIZATION OF CRUDE PETROLEUM HYDROCARBONS Frederick William Bertram Porter and Roy Purdy Northcott, Sunbury-on-Thames, England, assignors to The British Petroleum Company Limited Application January 22, 1953, Serial No. 332,661

Claims priority, application Great Britain January 28, 1952 2 Claims. (Cl. 208-218) This invention relates to the catalytic desulfurization of petroleum hydrocarbons by passing the hydrocarbons in admixture with hydrogen over a sulfur-resistant hydrogenation catalyst at elevated temperature and pressure such that organically-combined sulfur contained in the hydrocarbons is converted into hydrogen sulfide which may readily be removed from the treated hydrocarbons. Such a process may conveniently be called hydrofining. A typical temperature for the practice of the hydrofining process is 780 F. and a typical pressure 1000 lb./sq. in. Any sulfur-resistant hydrogenation catalyst may be used but particularly effective is a catalyst comprising the oxides of cobalt and molybdenum either as such or combined as cobalt molybdate, and preferably deposited on or incorporated with a support such, for example, as alumina.

The present invention is concerned with the application of the hydrofining process to petroleum feedstocks which under the normal conditions of the process are present in the reaction zone as a mixed gas/liquid phase. This condition applies particularly to the hydrofining of crude oil and crude oil residue.

We have found that changes in the hydrogen recycle rate when hydrofining crude oil have a marked and unexpected effect on the sulfur distribution. Thus, it was found that the sulfur content of the residue fraction of the hydrofined crude decreased, whereas the sulfur contents of the kerosene and gas oil fractions increased, with increase in recycle rate. It is believed that these changes in sulfur distribution are due primarily to changes in the gas/liquid phase ratio caused by alterations in the recycle rate. Thus, to take a specific example, at a recycle rate of 1000 s.c.f./b., 40% by volume of the crude is in the vapor phase, i.e. material boiling up to 275 C. and including the kerosene and about one-third of the gas oil, whereas at a recycle rate of 4000 s.c.f./b., 56% by volume of the crude is in the vapor phase, i.e.

material boiling up to 390 C. and including all the kerosene and gas oil and a small fraction of the residue. At the low recycle rate and at a space velocity for the crude oil of 2.0 v./v./hr., the gas oil is mainly in the liquid phase with a space velocity of 1.3 v./v./hr., whereas at the high recycle rate, it is wholly in the vapor phase, with a space velocity of 7.3 v./v./hr. resulting in less sulfur removal for the gas oil fraction. The kerosene is wholly in the vapor phase in both cases but at the low recycle rate, the sulfur content of the vaporized feed is 0.187% weight compared with 0.78% weight for the stocks which under the conditions necessary to bring 2,892,774 Patented June 30, 1959 about the reaction exist as a mixed gas/liquid phase, which results in greater overall desulfurization than is f at present possible.

I According to the present invention, a petroleum feedstock which under hydrofining conditions exists as a mixed gas/liquid phase is continuously separated into a gaseous fraction and a liquid fraction and the fractions passed continuously to separate hydrofining zones.

This method of operation enables the reaction conditions in the separate hydrofining zones to be adjusted to the optimum for both the gaseous and liquid fractions. In particular, the space velocity may be varied by adjusting the size of the effective catalyst volume.

The process may advantageously be operated with the recycle gas flowing in series through the two reactors. By this means the latent heat required to convert part of the feedstock into vapor may be supplied by the heat of reaction in the liquid phase reactor by flowing the recycle gas through a vapor disengaging zone intermediate the two reaction zones and into which the feedstock is fed.

The above method of operating the process may be carried into effect in various ways. Thus, the preheated feedstock may be passed to a disengaging zone wherein it is contacted with the hot recycle gases from the liquid phase reaction zone, whereby it is separated into a gaseous fraction and a liquid fraction, the gaseous fraction being passed with the recycle gases to a hydrofining zone, the products from which, after cooling, are separated into a desulfurized liquid product and a hydrogen-rich gaseous product, while the liquid fraction is passed through the liquid phase reactor in counter-current to the recycle gases and is then let down to atmospheric pressure and passed to a distillation zone, or, after cooling, to storage. Alternatively, the liquid fraction may be passed through the liquid phase reactor concurrently with the recycle gases, in which case the products leaving the reactor are passed to a hot separator operating at elevated pressure for the separation of the gases and vapors whereupon the liquid product is let down to atmospheric pressure as before.

In applying the process to crude petroleum or residue, the liquid fraction will contain any sodium and/ or vanadium contained in the crude petroleum or residue and although the quantities involved are small, they are sufiicient to cause a hydrofining catalyst of the cobalt molybdate type to lose activity, which loss in activity is not entirely regained on regeneration. The liquid phase reaction zone may therefore advantageously be formed in two parts, one of which contains a substance, such, as bauxite, capable of removing vanadium and/or sodium from the liquid fraction, while the other contains the hydrofining catalyst. The use of bauxite in this way for avoiding deactivation of a hydrofining catalyst forms the subject of copending application No. 276,256, filed March 13, 1952, now U.S. Patent No. 2,769,758.

The invention as applied to crude petroleum or residue will now be described by way of example with reference to the accompanying flow diagram.

The crude petroleum or residue passes via line 10 to furnace 11 wherein it is heated so that its temperature on leaving the furnace is 780 F. for example. From the furnace, the oil passes to a disengaging chamber 12 wherein it is contacted at a pressure of 1000 lb./sq. in.,

for example with the hot recycle gases entering via line 13. The gaseous fraction from the chamber 12 passes overhead via line 14 into a vapor phase reactor 15 maintained, for example, at 750 F. and 1000 p.s.i. wherein it is contacted with a sulfur-resistant hydrogenation catalyst, for example of the mixed cobalt and molybdenum oxide type. The products from the reactor 15 pass through a cooler 16 to a separator 17 from which a hydrogen-rich gas is taken overhead and passed to a vessel 18 for the removal of hydrogen sulfide after which the hydrogen-rich gasis recycled via line 19, make-up hydrogen.beingaddedvia line 20. .Desulfurizedliquid product is removed via line 21 and is passed todistillation unit. or otherwise disposed. of.

The liquid fractionfrom the chamber .12 is passed ,to a two-stage reactor system comprising the reactors 22 and 23 in series, one of Which is filled with bauxite and the other with hydrofining catalyst, for example of the mixed cobalt and molybdenum oxide type, and .both maintained at an elevated pressure of, for example 1000 lb./sq. in. Theliquid product may be .caused to flow downwardly through the reactors 22 and 23, asindicated by thefullline .24, in which case the reactor.22 contains bauxite and thereactor 23 hydrofining catalyst. The liquid product passes from reactor 23 via line 25 to a hot separator 26 wherein it is letdownto atmospheric pressure, the gaseous products passing via line 27 to a hydrogen recovery unit and the liquid product passing via line 28 to a vacuum distillation unit, or after cooling, to storage. Alternatively, the liquid product may be passed upwardly through the reactors 23 and 22 as indicated by broken line 29in which case thereactor 23 contains bauxite and the reactor 22 hydrofining catalyst. The liquid product leaves reactor 22 via line 30 and passes to a hot separator31 maintained under reactor pressure from which gaseous products are removed via line 32, and the'liquid product via line 33, the liquid product passing to hot separator 34 wherein it is let down -to atmospheric pressure, gaseous products passing via line 35 to a hydrogen recovery unit and liquid products via line 36 to a vacuum distillation unit or, after cooling, to storage.

The recycle gases from line 19 are passed through heater 37 from which they pass via line 38 at a temperature of, :forexample, 780 F. into the reactor 23. In the case of the down-flow reaction system,.the recycle gases pass out of the reactor 22 via lines 39 and 13 into the chamber 12 whilein the case of the up-flow reaction system the recycle gases flow intoline 13 from line 32.

Two examples of operation according to the invention will now be described.

Example I A Kuwait crude oil was split into a liquid fraction comprising 50% weight on the crude and a gaseous fraction comprising a gasoline fraction to 150 C., a kerosene fraction 150-230 C. and a gas oil fraction 230-350 C.

The liquid fraction was passed to the liquid phase reaction zone under the following conditions.

The gaseous fraction was passed to the vapor phase I reaction zone under the following conditions.

Temperature 750 F. Pressure 1000 p.s.i.ga. Space velocity "5.0 v.'/v./hr.

'4 I Recycle rate (based on crude) 4000 s.c.f./b. Catalyst Cobalt molybdate alumina. Catalyst life 10,000 hrs. (no regeneration).

The following results were obtained:

Feedstock Product Gasoline- 0.:

Percent wt. on crude 15. Sulfunpereent wt r 0 Kerosene-150430 0.:

Percent wt. on'crude 12. Sulfur, percent wt 0 Gas Ol1230350 0.:

Percent wt. on crude. Sulfur, percent wt...,

Example 11 A Kuwaitresidue (53 percent volume on crude) was split into a liquid fraction comprising 80 percent weight on the residue and a gaseous fraction comprising 20 percent weight on the residue.

The liquid fraction was passed to the liquid phase reaction .zone under the following conditions:

The gaseous fraction was passed to the vapor phase reaction zone under the following conditions:

Temperature ..750 F. Pressure ..-1000 p.s.i.ga. Space velocity 5.0 v./v./hr. Recycle rate (based ,on 53% residue) ..4000 s.c.f./b. Catalyst life .(cobalt molybdate on .alumina). 10,000 hours (no regeneration).

The following results were obtained:

Feedstock Product Percent wt.- on residue u 20 27 Sulfur; percent wt 2. 0 0.2

1 Gas oil over C.

We claim:

'1. A process for the hydrofining of crude oils and residues thereof containing at least about 20% vaporizable constituents, which comprises heating the feedstock to ,an elevated temperature at which-the feedstock is in the mixed gas/liquid phase, separating the heated feedstock into a gaseous fraction and a liquid fraction, passing the gaseous fraction toafirst hydrofining zone wherein it is contacted with a sulfur-resistant hydrogenation catalyst at elevated temperature and pressure such that the fraction is maintained substantially in the gaseous phase, passing the liquid fraction to a second hydrofining zone wherein it is contacted with a sulfur-resistant hydrogenationcatalyst' at elevated temperature and pressure such that the fraction is maintained substantially in the liquid phase, and recovering desulfurized liquid products from said hydrofining zones.

2. A process for the hydrofining of crude oils and residues thereof containing at least about 20% vaporizable constituents, which comprises heating the feedstock to an elevated temperature at which the feedstock is in the mixed gas/liquid phase, passing the heated feedstock to a vapor disengaging zone, passing the liquid product from said vapor disengaging zone to a first hydrofining zone wherein it is contacted with a sulfur-resistant hydrogenation catalyst at elevated temperature and pressure such that it is maintained substantially in the liquid phase, passing the vaporous product from said vapor disengaging zone to a second hydrofining zone wherein it is contacted with a sulfur-resistant hydrogenation catalyst at elevated temperature and pressure such that it is maintained substantially in the vapor phase, passing a hydrogen-containing recycle gas first through said first hydrofining zone, then through said vapor disengaging zone, and

finally through said second hydrofining zone, and recovering desulfurized liquid products from said hydrofining zones.

References Cited in the file of this patent UNITED STATES PATENTS 1,827,537 Morrell Oct. 13, 1931 1,881,534 Harding Oct. 11, 1932 2,025,255 Taylor et a1 Dec. 24, 1935 2,042,298 Davis May 26, 1936 2,070,295 Morrell Feb. 9, 1937 2,090,007 Mac Kenzie Aug.- 17, 1937 2,371,298 Hudson et al. Mar. 13, 1945 2,516,876 Home et a1. Aug. 1, 1950 2,516,877 Home et al. Aug. 1, 1950 2,574,446 Docksey et al. Nov. 6, 1951 2,587,987 Franklin Mar. 4, 1952 2,694,671 Baumgarten et al. Nov. 16, 1954 2,758,060 Porter et al. Aug. 7, 1956 

1. A PROCESS FOR THE HYDROFINING OF CRUDE OILS AND RESIDUES THEREOF CONTAINING AT LEAST ABOUT 20% VAPORIZABLE CONSTITUENTS, WHICH COMPRISES HEATING THE FEEDSTOCK TO AN ELEVATED TEMPERATURE AT WHICH THE FEEDSTOCK IS IN THE MIXED GAS/LIQUID PHASE, SEPARATING THE HEATED FEEDSTOCK INTO GASEOUS FRAACTION TO A FIRST HYDROFINING ZONE WHERE ING THE GASEOUS FRACTION TO A FIRST HYDROFINING ZONE WHEREIN IT IS CONTACTED WITH A SULFUR-RESISTANT HYDROGENATION CATALYST AT ELEVATED TEMPERATURE AND PRESSURE SUCH THAT THE FRACTION IS MAINTAINED SUBSTANTIALLY IN THE GASEOUS PHASE, PASSING THE LIQUID FRACTION TO A SECOND HYDROFINING ZONE WHEREIN IT IS CONTACTED WITH A SULFUR-RESISTANT HYDROGENATION CATALYST ATA ELEVATED TEMPERATURE AND PRESSURE SUCH THAT THE FRACTION IS MAINTAINED SUBSTANTIALLY IN THE LIQUID PHASE, AND RECOVERING DESULFURIZED LIQUID PRODUCTS FROM SAID HYDROFINING ZONES. 